Objective:To investigate the correlation between serum amyloid A protein(SAA)and growth differentiation factor-15(GDF-15)levels and the severity and prognosis of elderly patients with sepsis.Methods:80 elderly patients with sepsis were selected as the research subjects.According to the severity of sepsis,they were divided into sepsis group(n=36)and sep-tic shock group(n=44).According to the 28-day survival,the patients were divided into survival group(n=58)and death group(n=22).At the same time,healthy elderly people were selected as the control group(n=60).The serum indicators of SAA,GDF-15,white blood cell count(WBC),and neutrophil count(NEU)levels among different groups of subjects were com-pared,as well as the sequential organ failure score(SOFA)and acute physiology and chronic health status Ⅱ(APACHE Ⅱ)scores for different severity levels of sepsis.Spearman correlation analysis was used to analyze the correlation between serum in-dicators and SOFA and APACHE Ⅱ scores in sepsis patients,multivariate Logistic regression was used to analyze the factors affecting 28 day mortality in elderly sepsis patients,the predictive value of Receiver Operating Characteristic(ROC)curve was used to analyze the 28 day mortality in elderly sepsis patients.Results:Compared with the control group,the levels of SAA,GDF-15,WBC and NEU in septic shock group and sepsis group were increased(P<0.05).Compared with the sepsis group,the SOFA score,APACHE Ⅱ score,SAA,GDF-15,WBC and NEU levels in the septic shock group were increased(P<0.05).Spearman correlation analysis showed that SAA and GDF-15 levels were positively correlated with SOFA score(r=0.784,r=0.816,P<0.05)and APACHE Ⅱ score(r=0.757,r=0.793,P<0.05).Compared with the survival group,the SOFA score,APACHE Ⅱ score,SAA,GDF-15,WBC and NEU levels in the death group were increased(P<0.05).Multivariate Lo-gistic regression analysis showed that SAA(OR=1.551,P=0.003)and GDF-15(OR=1.826,P=0.001)were independent risk factors for 28-day death in elderly patients with sepsis.ROC curve analysis showed that the area under curve(AUC)of SAA for predicting 28-day mortality was 0.774,the AUC of GDF-15 was 0.806,and the AUC of the combined prediction was increased to 0.853.Conclusion:Serum SAA and GDF-15 levels are positively correlated with the severity of sepsis in elderly pa-tients,and the combination of the two has a high predictive value for the 28-day prognosis of patients.